Polarization-resolved output analysis of X-ray multiple-wave interaction

Abstract

The polarization suppression of the interfering components in X-ray multiple-wave interaction is observed for the first time by using a polarization analyzer with an arbitrary inclination of the diffraction plane with respect to that of the investigated crystal. The condition for total suppression of the multiple-wave interaction outside the investigated crystals by a polarization analyzer is derived theoretically from the modified Born approximation. By means of the partial suppression of the strong interfering component, the increase in the visibility of multiple-wave interference is experimentally and theoretically demonstrated. The proposed experimental polarization-resolved technique provides an operational way to enhance the visibility of X-ray multiple-wave interaction outside the investigated crystals for direct phase determination.

X-ray phase measurements as a probe of small structural changes in doped nonlinear optical crystals

“…Since it was reported decades ago that information on the phases of the structure factors -or more precisely, on invariant triplet phases -could be accessed via X-ray multiple diffraction (XRMD) experiments (Lipscomb, 1949;Hart & Lang, 1961;Post, 1977;Chapman et al, 1981;Chang, 1984;Shen & Colella, 1987), many attempts have been made to use this phenomenon as a physical solution of the phase problem in X-ray crystallography or, at least, as a general tool for studying crystalline and nonperiodic materials (Tischler & Batterman, 1986;Rossmanith, 1992;Weckert & Hü mmer, 1997;Avanci et al, 1998;Stetsko et al, 2000Stetsko et al, , 2001Shen et al, 2000;Remé dios et al, 2005). In this latter context, XRMD can be seen as a method to provide specific pieces of information that could not be retrieved by any other method and thus make it possible to distinguish one atomic structure from another among several possibilities.…”

Enhanced X-Ray Phase Determination by Three-Beam Diffraction

“…Very recently, several authors have demonstrated that the linear polarization of synchrotron radiation can be used to change the relative strength of multiple diffracted waves [14,15] and/or improve phase sensitivity in some cases [16]. Polarization resolved n-BD has also been considered for enhancing phase sensitivity [17]. However, phase determination is more complex than just carrying out measurements at optimized phase sensitive conditions.…”

“…The function f͑f͒ is the resonance term [11,13,17] describing the excitation of the secondary wave, D d , during the f rotation. In practice, simple functions can be used as the resonance term for fitting the azimuthal scans and extracting the triplet phases.…”

“…(1) is the interference term, the term that has the phase information and is responsible for the asymmetry in the three-BD profile. The optimal phase sensitive condition occurs when the wave fields are parallel, cosg 61 [18], and have nearly the same amplitude, jD p j ഠ jD d j [11,17].…”